Conventional manufacturing of decorative elastomeric (rubber) sheeting materials, strip-shaped sealing materials and the like, involves preparing a blank of uncured elastomer having a selected width, for example, 2 mm, using a calender method followed by a continuous vulcanization (curing) process. A common problem with this approach is that a substantial number of bubbles often form in the calendered blank. The bubbles may cause defects in a finished product produced from a calendered blank, such as, poor appearance, for example, unsightly surface blemishes, and/or could affect the operativeness of the product, for example, weakening or preventing proper sealing of a sealing tape. These common defects may also lead to waste, due to rejection of substantial quantities of such materials, during the manufacturing process.
The number and size of bubbles formed in the calendered blank is known to be linked to the composition, mixing conditions and viscosity of the uncured elastomer. However, limitations, such as, cost of materials, specifications for the appearance of a finished product, for example, optical clarity, and technical requirements of processing equipment; often restrict the alternatives available to a manufacturer in the selection of the uncured elastomer to be used to make a calendered product.
German Patent 36 23 795 (U.S. Pat. No. 4,826,638) is directed to making elastomeric products having a defined, irregular surface which is produced by mixing uncured elastomer with 5 to 60 parts hardened (cured) elastomer particles, per 100 parts uncured elastomer. The hardened elastomer particles are sized in the range of 0.1 mm to 1.0 mm and are made by cooling elastomer material in liquid nitrogen and grinding the cold material in a ball mill or impact pulverizer. Such a manufacturing process is uneconomical because it consumes large amounts of energy. The German Patent does not discuss bubble formation in the cured elastomer.